Can you take too many supplements? Why you might need to ditch the multivitamin

Katherine Isacks, MPS, RDN Registered Dietitian

Can you take too many supplements? Many of us have the mistaken assumption that if we need a little of something for health, then more is better. Is that true?

Is it true that you can take too many supplements?

Well, yes, if it concerns vitamins or minerals. Many of us have the mistaken assumption that if we need a little of something for health, then more is better. But getting too much of certain vitamins or minerals could be harmful. Of particular concern is getting a megadose or very large dose of a vitamin or mineral from a supplement.

Tolerable Upper Limit (UL)

According to the National Institutes of Health Office of Dietary Supplements, the Tolerable Upper Limit is the maximum daily intake unlikely to cause adverse health effects. Not all vitamins and minerals have a UL due to lack of data or no evidence of harm at high intakes.

Which vitamins can be toxic?

To find the UL for a nutrient in MyNetDiary, on the Dashboard, go to My Weight Plan, select Nutrient Targets, find the vitamin or mineral of interest, tap the 3-dot icon to the right of the name, and then select the "Target and Settings" option to view recommended intake as well as the UL. If the nutrient has a UL, it will be listed there.

If you take vitamin or mineral supplements, check the amount of each vitamin and mineral in your supplement against the UL value. Supplement manufacturers do not do this for you - they are not required to list the UL nor are they required to limit the amount of a nutrient to its UL. Many supplements contain well over the UL. Labels typically list the actual nutrient content as well as the % Daily Value (%DV) - a value used specifically for food labels to help consumers compare intake against a generic daily goal. The Daily Value for a nutrient could be higher or lower than a person's Recommended Dietary Allowance (RDA) for their age and sex group.

Is your supplement level higher than the upper limit?

The table below includes vitamins and minerals you can track in MyNetDiary and for which there is a UL. Because supplements never include this on their labels, the percentage of the UL value for each nutrient was calculated against its Daily Value. This percentage is represented in the last column as "% UL / Daily Value."

Rethink your supplement choice if the content of one or more nutrients is higher than the UL. The exception would be if you have been prescribed a high-dose vitamin or mineral supplement by your healthcare provider to correct a nutrient deficiency or to manage a chronic disease. Contact your healthcare provider if you are not sure about which vitamins might be toxic for you.

Upper limits for vitamins and minerals

Nutrient	UL Adults	Daily Value	% UL / Daily Value	Food content for comparison, per 100 grams
Folate	1000 mcg	400 mcg	250%	Asparagus, 149 mcg
Niacin	35 mg	16 mg	218%	Turkey, 10 mg
Vit B6	100 mg	1.7 mg	5882%	Chicken, 0.5 mg
Vit C	2000 mg	90 mg (males) 75 mg (females)	2222%	Bell pepper, 80 mg
Vit A	3000 mcg	900 mcg (males) 700 mcg (females)	333%	Carrots, 835 mcg
Vit D	100 mcg (4000 IU)	15 mcg (600 IU)	666%	Mushrooms, 0.2 mcg (81 IU)
Vit E	1000 mg	15 mg	6666%	Almonds, 8 mg
Calcium	2500 mg age 19-50 yr 2000 mg age > 50 yr	1000 mg (males) 1200 mg (females)	208% age 19-50 yr 166% age > 50 yr	Milk, 300 mg
Copper	10,000 mcg	900 mcg	1111%	Oysters, 4.5 mg
Iron	45 mg	8 mg (males) 18 mg (females)	250%	Lentils, 7 mg
Magnesium	350 mg	420 mg (males) 320 mg (females)	83%	Pumpkin seeds, 150 mg
Manganese	11 mg	2.3 mg (males) 1.8 mg (females)	478%	Pecans, 4.5 mg
Phosphorus	4000 mg age 19-70 yr 3000 mg age > 70 yr	700 mg	571% age 19-70 yr 429% age > 70 yr	Sunflower seeds, 200 mg

Source: National Institutes of Health Office of Dietary Supplements

Supplement form vs. food source

For certain nutrients, the UL only applies to the synthetic form of the vitamin found in supplements or fortified food sources that can cause risk in high doses. This is true for vitamins A, E, niacin, and folate, and magnesium. Nutrients coming from natural food sources are rarely the cause of nutrient toxicity.

Magnesium

Are you surprised that the UL is lower than the Daily Value? This is not an error and the reason is simple. The tolerable upper limit (UL) applies only to magnesium coming from supplements and medications. Too much magnesium from supplements and medications can cause adverse health effects such as diarrhea, nausea, and cramping. But the good news is that there is no UL for magnesium that comes from food or water.